近周边视网膜区模糊认知感的研究

目的 :介绍作者所在的实验中心近年来对于黄斑区和近周边视网膜区 (≤ 8°)模糊认知感的研究结果。方法和结果 :先后介绍三个实验。实验一测量了近周边视网膜区的焦深 (即对视网膜离焦的主觉耐受程度 ) ,并将其与黄斑区的反应进行了比较。实验二测量了近周边视网膜区的模糊敏感阈值和模糊辨别阈值。上述两实验结果表明 ,人眼焦深在近周边视网膜区随其与黄斑的距离增大而逐渐升高 ,其值从黄斑区的 0 .89D增加到距黄斑 8度视角离心区的 3.51D。模糊敏感阈值 ,即导致初始模糊认知感的视网膜离焦度 ,也随其与黄斑的距离增大而逐渐升高 ;其值从黄斑区的 0 .85D增加到距黄斑 8度视角离心区的 1 .89D。模糊辨别阈值 ,即在初始模糊认知感的条件下觉察初始模糊程度改变的视网膜离焦度 ,同样亦随其与黄斑的距离增大而逐渐升高 ,其值从黄斑区的 0 .4 5D增加到距黄斑 8度视角离心区的 0 .93D。基于实验一 ,二的结果 ,作者设计了实验三 :通过测量视标大小对焦深的影响以研究近周边视网膜区和黄斑区对模糊认知感的综合效应。结果表明 ,人眼焦深在近周边视网膜区随着视标尺寸的增大而逐渐升高 ,且据其数据分析结果及回归方程斜率的个体差异性 ,可将总体实验对象区分为两个亚组 :即“黄斑主导型”和“黄斑 周边视网膜协

Recent studies on blur perception in the near retinal periphery

Objective:This paper reviews recent findings in our laboratory on blur perception in the fovea and in the near retinal periphery(up to 8 degrees).Two parameters were investigated:①blur detection,which is the perceptual tolerance to retinal defocus and is related to the depth-of-focus(DOF):blur is perceived if tolerance is exceeded,and ②Blur discrimination,which is the just noticeable difference(jnd) in blur.Methods and Results:①In the first experiment,the DOF was measured in the near retina periphery and compared to the foveal response.The total DOF increased from 0.89 D in the fovea to 3.51 D at 8 degrees of retinal eccentricity.②In the second experiment,blur detection and initial blur discrimination thresholds were assessed in the near retinal periphery.The blur detection threshold increased from 0.85 D in the fovea to 1.89 D at 8 degrees of retinal eccentricity.The initial blur discrimination threshold increased from 0.45 D in the fovea to 0.93 D at 8 degrees of retinal eccentricity.③In the third experiment,the total DOF was measured as a function of target size across the near retinal periphery.It progressively increased with target size.Based on an analysis of individual subject data and their related regression slopes,the subject population was divided into two subgroups:a predominantly foveally driven(F only) subgroup and a foveally+peripherally driven(F+P) subgroup.Conclusion:We speculate that the reduced blur sensitivity found in the near retinal periphery may be attributed to related changes in cone density,perceptual sharpness overconstancy,optical aberrations,and visual attention in peripheral vision.The more sensitive blur discrimination versus blur detection findings may be attributed to variation in the optical MTF function in retinal defocus and to a perceptually based blur buffering mechanism.The increased depth-of-focus with larger target sizes suggested cone pooling of blur information across the near retinal periphery.